Transistors are commonly utilized in integrated circuitry. For instance, transistors can be utilized in memory arrays, and/or in logic circuitry peripheral to a memory array. Two common types of transistors are p-type metal-oxide-semiconductor field effect transistors (PMOSFETs) and n-type metal-oxide-semiconductor field effect transistors (NMOSFETs). PMOSFETs can be referred to as PMOS transistors, and NMOSFETs can be referred to as NMOS transistors. In some applications, an NMOS transistor can be paired with a PMOS transistor in a complementary metal-oxide-semiconductor (CMOS) assembly.
A continuing goal of semiconductor processing is to reduce process steps. Accordingly, it can be desired to utilize common process steps for fabrication of portions of NMOS transistors and PMOS transistors, so that portions of the NMOS transistors can be fabricated simultaneously with portions of the PMOS transistors.
It is also a continuing goal to fabricate transistors tailored for the particular applications of the transistors, and specifically to tailor the work functions of the transistors.
It would be desired to develop methods of semiconductor fabrication which can simultaneously form portions of NMOS transistors and portions of PMOS transistors, while also enabling work functions of the various transistors to be tailored for the applications of the transistors.